public class MD5 {

    /* 下面這些S11-S44實際上是一個4*4的矩陣，在原始的C實現中是用#define 實現的,這里把它們

    /* 實現成為static final是表示了只讀，切能在同一個進程空間內的多個Instance間共享*/

    static final int S11 = 7;

    static final int S12 = 12;

    static final int S13 = 17;

    static final int S14 = 22;


    static final int S21 = 5;

    static final int S22 = 9;

    static final int S23 = 14;

    static final int S24 = 20;


    static final int S31 = 4;

    static final int S32 = 11;

    static final int S33 = 16;

    static final int S34 = 23;


    static final int S41 = 6;

    static final int S42 = 10;

    static final int S43 = 15;

    static final int S44 = 21;

    static final byte[] PADDING = {-128, 0, 0, 0, 0, 0, 0, 0, 0,

                                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

                                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

                                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

    /* 下面的三個成員是MD5計算過程中用到的3個核心數據，在原始的C實現中 */

    /*   被定義到MD5_CTX結構中 */

    private long[] state = new long[4];  // state (ABCD)

    private long[] count = new long[2];  // number of bits, modulo 2^64 (lsb first)

    private byte[] buffer = new byte[64]; // input buffer

    /* digestHexStr是MD5的唯一一個公共成員，是最新一次計算結果的16進制ASCII表示. */

    public String digestHexStr;

    /* digest,是最新一次計算結果的2進制內部表示，表示128bit的MD5值. */

    private byte[] digest = new byte[16];


    /*  getMD5ofStr是類MD5最主要的公共方法，入口參數是你想要進行MD5變換的字符串 */

    /*  返回的是變換完的結果，這個結果是從公共成員digestHexStr取得的．*/

    public String getMD5ofStr(String inbuf) {

        md5Init();

        md5Update(inbuf.getBytes(), inbuf.length());

        md5Final();

        digestHexStr = "";

        for (int i = 0; i < 16; i++) {
            digestHexStr += byteHEX(digest[i]);
        }

        return digestHexStr;
    }
    
    public String getMD5ofStr(byte[] inbuf)
    {

        md5Init();

        md5Update(inbuf, inbuf.length);

        md5Final();

        digestHexStr = "";

        for (int i = 0; i < 16; i++) {
            digestHexStr += byteHEX(digest[i]);
        }

        return digestHexStr;
    }     

    /* 這是MD5這個類的標準構造函數，JavaBean要求有一個public的并且沒有參數的構造函數. */

    public MD5() {
        md5Init();
    }

    /* md5Init是一個初始化函數，初始化核心變量，裝入標準的幻數 */
    private void md5Init() {

        count[0] = 0L;

        count[1] = 0L;

        ///* Load magic initialization constants.

        state[0] = 0x67452301L;

        state[1] = 0xefcdab89L;

        state[2] = 0x98badcfeL;

        state[3] = 0x10325476L;

        return;

    }

    /* F, G, H ,I 是4個基本的MD5函數，在原始的MD5的C實現中，由于它們是 */

    /* 簡單的位運算，可能出于效率的考慮把它們實現成了宏，在java中，*/

    /* 我把它們實現成了private方法，名字保持了原來C中的。 */
    private long F(long x, long y, long z) {
        return (x & y) | ((~x) & z);
    }


    private long G(long x, long y, long z) {
        return (x & z) | (y & (~z));
    }


    private long H(long x, long y, long z) {
        return x ^ y ^ z;
    }


    private long I(long x, long y, long z) {
        return y ^ (x | (~z));
    }


    /* FF,GG,HH和II將調用F,G,H,I進行近一步變換 FF, GG, HH, and II transformations */

    /* for rounds 1, 2, 3, and 4. Rotation is separate from addition to prevent recomputation. */
    private long FF(long a, long b, long c, long d, long x, long s, long ac) {

        a += F(b, c, d) + x + ac;

        a = ((int) a << s) | ((int) a >>> (32 - s));

        a += b;

        return a;
    }


    private long GG(long a, long b, long c, long d, long x, long s, long ac) {

        a += G(b, c, d) + x + ac;

        a = ((int) a << s) | ((int) a >>> (32 - s));

        a += b;

        return a;
    }


    private long HH(long a, long b, long c, long d, long x, long s, long ac) {

        a += H(b, c, d) + x + ac;

        a = ((int) a << s) | ((int) a >>> (32 - s));

        a += b;

        return a;
    }


    private long II(long a, long b, long c, long d, long x, long s, long ac) {

        a += I(b, c, d) + x + ac;

        a = ((int) a << s) | ((int) a >>> (32 - s));

        a += b;

        return a;
    }


    /* md5Update是MD5的主計算過程，inbuf是要變換的字節串，inputlen是長度，這個 */

    /* 函數由getMD5ofStr調用，調用之前需要調用md5init，因此把它設計成private */
    private void md5Update(byte[] inbuf, int inputLen) {

        int i, index, partLen;

        byte[] block = new byte[64];

        index = (int) (count[0] >>> 3) & 0x3F;

        // /* Update number of bits */

        if ((count[0] += (inputLen << 3)) < (inputLen << 3))

            count[1]++;

        count[1] += (inputLen >>> 29);

        partLen = 64 - index;

        // Transform as many times as possible.

        if (inputLen >= partLen) {

            md5Memcpy(buffer, inbuf, index, 0, partLen);

            md5Transform(buffer);

            for (i = partLen; i + 63 < inputLen; i += 64) {

                md5Memcpy(block, inbuf, 0, i, 64);

                md5Transform(block);

            }

            index = 0;

        } else

            i = 0;

        ///* Buffer remaining input */

        md5Memcpy(buffer, inbuf, index, i, inputLen - i);

    }


    /* md5Final整理和填寫輸出結果 */
    private void md5Final() {

        byte[] bits = new byte[8];

        int index, padLen;

        ///* Save number of bits */

        Encode(bits, count, 8);

        ///* Pad out to 56 mod 64.

        index = (int) (count[0] >>> 3) & 0x3f;

        padLen = (index < 56) ? (56 - index) : (120 - index);

        md5Update(PADDING, padLen);

        ///* Append length (before padding) */

        md5Update(bits, 8);

        ///* Store state in digest */

        Encode(digest, state, 16);

    }


    /* md5Memcpy是一個內部使用的byte數組的塊拷貝函數，從input的inpos開始把 */

    /* len長度的字節拷貝到output的outpos位置開始. */
    private void md5Memcpy(byte[] output, byte[] input, int outpos, int inpos, int len) {
        int i;

        for (i = 0; i < len; i++)
            output[outpos + i] = input[inpos + i];
    }


    /* md5Transform是MD5核心變換程序，有md5Update調用，block是分塊的原始字節. */
    private void md5Transform(byte block[]) {
        long a = state[0], b = state[1], c = state[2], d = state[3];

        long[] x = new long[16];


        Decode(x, block, 64);

        /* Round 1 */

        a = FF(a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */

        d = FF(d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */

        c = FF(c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */

        b = FF(b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */

        a = FF(a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */

        d = FF(d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */

        c = FF(c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */

        b = FF(b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */

        a = FF(a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */

        d = FF(d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */

        c = FF(c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */

        b = FF(b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */

        a = FF(a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */

        d = FF(d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */

        c = FF(c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */

        b = FF(b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */

        /* Round 2 */

        a = GG(a, b, c, d, x[1], S21, 0xf61e2562L); /* 17 */

        d = GG(d, a, b, c, x[6], S22, 0xc040b340L); /* 18 */

        c = GG(c, d, a, b, x[11], S23, 0x265e5a51L); /* 19 */

        b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL); /* 20 */

        a = GG(a, b, c, d, x[5], S21, 0xd62f105dL); /* 21 */

        d = GG(d, a, b, c, x[10], S22, 0x2441453L); /* 22 */

        c = GG(c, d, a, b, x[15], S23, 0xd8a1e681L); /* 23 */

        b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L); /* 24 */

        a = GG(a, b, c, d, x[9], S21, 0x21e1cde6L); /* 25 */

        d = GG(d, a, b, c, x[14], S22, 0xc33707d6L); /* 26 */

        c = GG(c, d, a, b, x[3], S23, 0xf4d50d87L); /* 27 */

        b = GG(b, c, d, a, x[8], S24, 0x455a14edL); /* 28 */

        a = GG(a, b, c, d, x[13], S21, 0xa9e3e905L); /* 29 */

        d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8L); /* 30 */

        c = GG(c, d, a, b, x[7], S23, 0x676f02d9L); /* 31 */

        b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL); /* 32 */

        /* Round 3 */

        a = HH(a, b, c, d, x[5], S31, 0xfffa3942L); /* 33 */

        d = HH(d, a, b, c, x[8], S32, 0x8771f681L); /* 34 */

        c = HH(c, d, a, b, x[11], S33, 0x6d9d6122L); /* 35 */

        b = HH(b, c, d, a, x[14], S34, 0xfde5380cL); /* 36 */

        a = HH(a, b, c, d, x[1], S31, 0xa4beea44L); /* 37 */

        d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9L); /* 38 */

        c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60L); /* 39 */

        b = HH(b, c, d, a, x[10], S34, 0xbebfbc70L); /* 40 */

        a = HH(a, b, c, d, x[13], S31, 0x289b7ec6L); /* 41 */

        d = HH(d, a, b, c, x[0], S32, 0xeaa127faL); /* 42 */

        c = HH(c, d, a, b, x[3], S33, 0xd4ef3085L); /* 43 */

        b = HH(b, c, d, a, x[6], S34, 0x4881d05L); /* 44 */

        a = HH(a, b, c, d, x[9], S31, 0xd9d4d039L); /* 45 */

        d = HH(d, a, b, c, x[12], S32, 0xe6db99e5L); /* 46 */

        c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8L); /* 47 */

        b = HH(b, c, d, a, x[2], S34, 0xc4ac5665L); /* 48 */

        /* Round 4 */

        a = II(a, b, c, d, x[0], S41, 0xf4292244L); /* 49 */

        d = II(d, a, b, c, x[7], S42, 0x432aff97L); /* 50 */

        c = II(c, d, a, b, x[14], S43, 0xab9423a7L); /* 51 */

        b = II(b, c, d, a, x[5], S44, 0xfc93a039L); /* 52 */

        a = II(a, b, c, d, x[12], S41, 0x655b59c3L); /* 53 */

        d = II(d, a, b, c, x[3], S42, 0x8f0ccc92L); /* 54 */

        c = II(c, d, a, b, x[10], S43, 0xffeff47dL); /* 55 */

        b = II(b, c, d, a, x[1], S44, 0x85845dd1L); /* 56 */

        a = II(a, b, c, d, x[8], S41, 0x6fa87e4fL); /* 57 */

        d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0L); /* 58 */

        c = II(c, d, a, b, x[6], S43, 0xa3014314L); /* 59 */

        b = II(b, c, d, a, x[13], S44, 0x4e0811a1L); /* 60 */

        a = II(a, b, c, d, x[4], S41, 0xf7537e82L); /* 61 */

        d = II(d, a, b, c, x[11], S42, 0xbd3af235L); /* 62 */

        c = II(c, d, a, b, x[2], S43, 0x2ad7d2bbL); /* 63 */

        b = II(b, c, d, a, x[9], S44, 0xeb86d391L); /* 64 */


        state[0] += a;

        state[1] += b;

        state[2] += c;

        state[3] += d;

    }


    /* Encode把long數組按順序拆成byte數組，因為java的long類型是64bit的，*/

    /* 只拆低32bit，以適應原始C實現的用途. */
    private void Encode(byte[] output, long[] input, int len) {

        int i, j;

        for (i = 0, j = 0; j < len; i++, j += 4) {

            output[j] = (byte) (input[i] & 0xffL);

            output[j + 1] = (byte) ((input[i] >>> 8) & 0xffL);

            output[j + 2] = (byte) ((input[i] >>> 16) & 0xffL);

            output[j + 3] = (byte) ((input[i] >>> 24) & 0xffL);

        }

    }


    /* Decode把byte數組按順序合成成long數組，因為java的long類型是64bit的，*/

    /* 只合成低32bit，高32bit清零，以適應原始C實現的用途. */
    private void Decode(long[] output, byte[] input, int len) {

        int i, j;

        for (i = 0, j = 0; j < len; i++, j += 4)

            output[i] = b2iu(input[j]) |

                    (b2iu(input[j + 1]) << 8) |

                    (b2iu(input[j + 2]) << 16) |

                    (b2iu(input[j + 3]) << 24);

        return;

    }


    /* b2iu是一個把byte按照不考慮正負號的原則的＂升位＂程序，因為java沒有unsigned運算 */
    public static long b2iu(byte b) {

        return b < 0 ? b & 0x7F + 128 : b;

    }

    /* byteHEX()，用來把一個byte類型的數轉換成十六進制的ASCII表示，*/

    /* 因為java中的byte的toString無法實現這一點，我們又沒有C語言中的sprintf(outbuf,"%02X",ib). */
    public static String byteHEX(byte ib) {

        /* if want to output normal letter please user DigitNormal */

        char[] DigitNormal = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

                              'a', 'b', 'c', 'd', 'e', 'f'};

        /* if want to output capitalization letter please user DigitCap */

        /* char[] DigitCap = { '0','1','2','3','4','5','6','7','8','9',

        'A','B','C','D','E','F' }; */

        char[] ob = new char[2];

        ob[0] = DigitNormal[(ib >>> 4) & 0X0F];

        /* ob[0] = DigitCap[(ib >>> 4) & 0X0F]; */

        ob[1] = DigitNormal[ib & 0X0F];

        /* ob[1] = DigitCap[ib & 0X0F]; */

        String s = new String(ob);

        return s;
    }


    public byte[] getMD5(byte[] data1 , byte[] data2) {
        md5Init();

        md5Update(data1, data1.length);

        md5Update(data2, data2.length);

//        md5Update(Request.key , Request.key.length);

        md5Final();

        return digest;
    }

}